Engine indicator and spark plug



May 3l, 1932. E. J. MARTIN 1,861,021

ENGINE INDICATOR AND SPARK PLUG Filed Jan. 24, 1929 aww/mag Patented May; 3,1, 1932 UNITED STATES PATENT oFFicE EDWARD I; MARTIN, or DETROIT, MICHIGAN, AssIGNoE ToGENEEaL morons RE- f SEARCH CoRPoEATIoN, CF DETaom'MICHIGAN, A` CORPORATION or DELAWARE ENGINE INDICATOR AND. spar-1I` PLUG Application fied :nuary 24, 1929,V serial-N. 334,665.

` This inventionhas to do with engine indii caters of the'type-disclosed and claimed in my prior application Serial No. 265,452, filed March 28,1928. A

` lVhile the indicator disclosedin-my prior application operated very satisfactorily -it possessed the disadvantage that it was necesv. sary to provide a special hole in the cylinder or cylinder head toreceive it. vAccording to o -my improved design, niy engine indicator is -combined with a spark plug so that to make use of my indicator` 'itis simply necessary to .replace the conventional spark plug ivith Amy improvedcombination spark *plug and indicator. I f

As in my prior design, I' have provided an' arrangement for cooling` theddiaphragin by means of a current of air or other vcooling fluid@ According to my Aimproved ar- 2o rangement the cooling' stream is circulated about the central insulated electrode of the plug, insuringthat it will notp'bccome so heated as to cause preig'nition. Referring .to the drawings:

v 26 Flgure 1 is a view,r partly in seetionfshoiving' .my improved combination sparkp lug j and indicator applied to an internal combus- V-tion engine, and also, diagrammatically, the

circuit with which ,the indicator lis used.

Figure 2 is a view similar to Figure 1 but taken at-right angles to-l that figure'. Figure 3 is a-section, online 3%-3 of Figure 1.

10 represents a portion ofthe cylinder hea-d of an interna-l eombustionengine of conven? tional ltype and 12 indicates the usual threaded aperturel providedi'n .the .head for the reception of the conventionaltype of spark Y plug. 14 indicates, as an entirety, my com` bined spark plug and engine indicator. .This `device comprises a frame16 provided with a threaded .extension 18 for `en,f fa rement inthe aperture 12. The frame 16 is provided with a central bore'20 to receive the central electrode of the spark plug, the spark plug inborethe Vframe 16` is provided with a large recess or cavity 22 into which extends a rigid arm 24 integral with the frame. The arm 24 is provided with an aperture in registrationwvith the bore 20 in the frame 16. The lower end of the bore 20 is sealed by means of a diaphragm 26 which may be secu-red to .the frame 16 by-weldi-n,-g,"or brazing.` The to the diaphragn'i by forming the lower end.

'with a channel 32 into which edges of the diaphragm are fitted,'\vhereupo1 i t-he walls of the channel are clinched about it. Obviously the connection may -be accomplished .by welding or brazing if preferred, the only requirement being that the connection shall he secure and gas tight.` vThe up er end lof the tube 30 is threaded and is rigi ly secured to the arm '24.by means of clamping nuts l 33 as shown;l I

It is .now obvious that with this arrangement movementof the diaphragm 26 is transmitted by the tubular thrust member 30 to the frigid arm 24 and this effects operation of the' indicating mechanism which is substantially the samel as that shown in'iny prior applica'- tion and now to khe briefly described. The

arm -34 is referred to hereinafter as the indicating means since all indications result fromthe slight movement given to it and the vheatstone bridge. oscillograph, .and other elements of the indicating mechanism merely serve to magnify and analyze its movement.

0n 'opposite s'idesof` the rigid arm 24 are arranged carbon pile rheosta'ts 34 and 36. The rheostatsconsist of c arbon disks clamped between .end plates. The end plates remote from the rigid arm'are provided With conical' recesses 38 to receive the conical ends of adjustable screws- 40 threaded in the frame 16.

Lock nuts 42 are provided to hold the screws in adjusted position. The adjacent end plates are provided with integral conical studs 44 which engage in lrecesses formed in lo'ppositesides of the rigid'arm 24. The remote end plates are' insulatedfrom the frame 16 by means of interposed .insulating disks to the ends of fixed resistances 62 and 64 res pectively. Conductor 66 leads from the terminal 54 through the oscillograph element 68 to conductor 70 connecting the adjacent ends of the fixed resistances.

,Rheostat 34, terminal 52, and conductor 58 constitute one leg of a Wheatstone bridge.

Rheostat 36, terminal 56, and conductor 60..

constitute another leg of a VVVheatstonebridge in series with the first leg. The other legs of the bridge are constituted by the fixed re'- sistancesl 62 and 64. The bridging circuit consists of the rigidV arm 24, frame 16, terminal 54, conductor 66, and oscillograph element 68. Current is'supplied to the Wheatstone bridge from battery 72 through variable resistance 74 and. conductors 76 and 7 8. The oscillograph clement, which is but diagrammatically indicated, produces movement of a mirror in synchronism with the current fluctuations in the bridgingcircuit, causing a light ra to be projected and re- -corded on a traveling photographic roll.

The operation of the indicating mechanism is as follows: Pressure variationsin the combustion chamber cause movement of the diaphragm 26 which is. transmitted through the t-ubular thrustv member 30 to the rigid arm 24.` Movement of the arm effects variations in the pressure applied to the carbon pile rheostats 34 and 36 and this results in corre- -sponding variations in their resistance and, consequently, in the potential at that end of the bridging circuit, causing 'fiow of current through the bridging circuit which operates the oseillograph element 68. The' movement of theelement is recorded on the photographic roll and gives an accurate record of pressure variations in the combustion chamber.-

. lVith in the tubular thrust member 30 there is arranged an insulator 80 surrounding the central electrode 82 :of the spark plug. At the upper end of the bore there is provided a second'insulator 84 surrounding the first insulator and centering it in the bore of the member 16. The central electrode is provided with the usual terminal 86 which may beV connected in the usual` manner to the ignitionl system. The side electrode 88 which cooperates with the central electrode :is preferably mounted on the diaphragm 26 although it might, if preferred, be mounted4 di- 5 rectly on the member 16.

I have shown at 90 a bore communicating with the central bore 20 and connected at 92 to a conduit leading to a source of compressed air. `A cooling blast of air isthus directed against thediaphragm, the air escaping through the clearance provided between the tubular' thrust member 30 and the bore 20 into the chamber 22 from which it mayescapc through suit-able apertures, not shown, into the atmosphere. The cooling blast not only cools the diaphragm but. also cools the central electrode and its insulator, preventing pre-l ignition.

I claim 1. A combined spark plug and engine indicator comprising a member provided with ihrarm and the ri d member an an insul lated electrode mounted in the bore and e.\

tending through the diaphragm, said electrede being provided at its upper end with means adapted for connection with a source of electric current.

2. A combined spark plug and engine indicatorcomprising a member provided with a bore therein and with a rigid indicating member intercepting the bore and provided with an aperture aligned with the bore, a. diaphragm at one end of the bore, a tubular thrust member rigidly connecting the diaphragm and the rlgid member, and an insulated elect-rode mounted in the bore andpextending through the diaphragm, said electrode being provided at its upper end with means adapted for connection with a source of electric current, said member bein provided with a passage for the projection of cooling fiuid on the diaphragm, said tubular member loosely fitting the bore to form a passage for thediseharge of cooling fluid.

3. spark plug comprising a central insulated electrode and a side electrode, said plug being provided with passages for circulating a coolin fluid about said central electrode, and wit an outlet passage for the discharge of fluid therefrom and .means for supplying flnid'under pressure to said pas- Isages. j

4. A pressure indicator comprising a fitting'adapted to be secured in an aperture in the wall of a pressure chamber and compris` ing a rigid indicating element having a free end, a tubular thrust member rigidly connected to the free end of said element and having its lower end extending into the cham` ber, and an annular diaphragm rigidly secured tothe lower end of the tubular thrust member and having an annularly distended portion exposed in the chamber and a cons tricted neck portion fixed to 'the fitting.

5. An engine indicator comprising a fitting adapted to be secured within an aperthe dinleu llt

ture in the Wall of a pressure chamber, said fitting being provided with a bore therein and with a rigid arm extending'transversely of the bore, a diaphragm closing the end of the bore exposed in the chamber, a rigid tubular thrust member connecting the diaphragm and arm, an electrode housed .vithin the thrust member and projecting through opposite ber, a rigid tubular thrust member connect-y ing the diaphragm and arm. an lelectrode housed within the .thrust member and projecting through opposite endsof the bore, a tubular insulator insulating the electrode from the thrust member. a second insulator mounted in the upper end of the bore and insulating the electrode from thel fitting, said arm being adapted for connection with means for amplifying and displaying the character of the vibrations impartedto said thrust-member by pressure variations 'in the chamber.

7. An engine indicator comprising an integral fitting adapted to be secured within an` aperture in thel Wall of a pressure chamber, said Afitting being provided with a bore therein, and said bore being enlarged intermediate its ends, a diaphragm closing the end 'of the bore exposedsin the pressure chamber,l said fitting being provided with an integral arm extending into the enlarged portion of the bore and at a point remote from the exposed end of the bore. a tubular thrust member connecting the diaphragm and arm. an electrode housed Within the thrust member and pro*- iecting through opposite ends of thel bore. a tubular insulator insulating the electrode from the thrust member. said arm beingadapted for connection with means for amplifying and displaying the character of the Vibrations imparted to said thrust member 'by pressure variations in the chamber;

8. An engineindicator comprising a fitting' adapted to be' secured within any aperture in A-the'wall of aA pressure chamberssaid fitting beingprovided with a borethereinand said bore being enlarged intermediate lts ends. a

diaphragm .closing the end of the bore ex# posedin the pressure chamber. said fitting being provided with an arm extending into the enlarged portion of the bore and at a point remote from the exposed end of the 55 bore, a tubular thrust member connecting-the diaphragm and arm, an electrode housed within the thrust member and projecting through opposite ends ofthe bore, a tubular insulator insulatin the electrode from the thrust member, an a pressure sensitive elementhoused within the enlarged portion of the bore.

9. A combined spark plug andengine indicator comprising a tubular shell adapted to be secured in the usual spark plug aperture in the wall of the combustion chamber of an internal combustion engine, a central elec.- trode in the shell provided at its upper end with means for connection with a source of current, an insulator within the shell surrounding theelectrode, a second electrode in conductive relation with the shell and providingin conjunction'l with the lower end of the first named electrode a -spark .gap normally exposed in the combustion chamber, a

lmovable Wall member surrounding the insulator and in sealing relation with the shell, indicating means, and means directly connecting said movable Wall member with said indicating means so that the motion of the wall member in response to pressure variations in the chamber is transniitted to the indicating means independently of said insulator.

10. A combined spark plug and engine indicator comprising a tubular shell adapted to be secured in the usual spark plugaperture in the wall of the combustion chamber of an internal combustion' engine, a central elec'- trode in the shell provided at its upper end with means' for connection with a source of current, an insulator within the shell surrounding the electrode, a second electrode in conducting relation with said shell and providing in conjunction vith the lower end of the first named electrode a spark gap normally exposed in the combustion chamber, a movable diaphragm surrounding the insulator and secured tothe shell, indicating means, and means directly and rigidly connecting said movable Wa-llmember with said indicatlng meansl soth'at the motion of' the diaphragm in response `to pressure variations in the chamber is transmitted to the indicating 4means independently of said insulator.

11.l A combined spark plug and engine indicator comprising a tubular shell adapted to be secured in the usual spark plug'aperture in the wall of the combustion chamber,

a central electrode in theshell 'provided at its upper end with means for connection with a source of current, an insulator within the shell-surrounding the electrode, a second electrode in conducting relation with the shell and providing in conjunction with the lower end of the Yifirst named electrode 'a spark gap normally exposed in the combustion chamber, a movable Wall member surrounding the insulator and in sealing rela-y y tion with the shell, indicating means includshell surrounding the electr-(ale, a second elecing a rigid arm, and means directly and rigidly connecting said movable wall member with said indicating means so that the motion of the wall member in response to pres- 5 sure variations in the chamber is transmitted to the indicating means independently of said insulator. A 12. A combined spark plug and engine indicator comprising a tubular shell adapted 0 to be secured in the usual spark plug aperture in the Wall of the combustion chaml er, `a center electrode in the shell provided at its upper end with means for connection with a source of current, an insulator Within the trode in conductive 'relation with said shell and provldmg 1n comunetlon with the lower end of the first named electrode a-spark gap normally exposed inthe combustion chamber, a tubular thrust member surrounding thevinsulator, a movable wall member lse- 'cured to the thrust member and in sealing relation with the shell, indicating means,

said tubular thrustfmember being directly and rigidly connected to said indicating means so that motion of the wall member 1n response to pressure variations 1n the chamber" is transmitted to the indicating means independently of said insulator.

13. A combined spark plug and engine indicator comprising a tubular shell adapted to be secured in the usualspark plug aperturevin the wall of the combustion chamber, a center electrode in the shell provided at its u upper end with means for connection with a source of current, aninsulator within the shell surrounding the electrode, a tubular thrust member surrounding the insulator, a diaphra m secured to the thrust member and to the s ell, a second electrode moimted on the diaphragm and providing in conjunction with the lower end of the iirstnamed insulator, a spark gap normally exposed in 5 a center electrode inthe shell provided at its upper end with means for connection with 'a source of current, an insulator within the shell surrounding the electrode, a second electrode in conductive relation with said shell and providing in conjunctionv with the lower end ofthe first named electrode a spark gap normally exposed in the combustionehamber, a tubular thrust member surrounding the insulator, a movable wall member secured to the thrust member and in sealing relation with the shell, indica means inlated electrode mounted in the bore and extending through the diaphragm, said electrode being provided at its upper end with means adapted for connection with a source of electric current.

1 6. A' pressure indicator com risin a member adapted for insertion in e wa of a pressure chamber and rovided with a bore therein and with a rigi( indicatin arm extending adjacent the bore, a tubu ar thrust member extending through the bore and rigidly connected with the arm, an annular diaphragm' connecting the thrust member and the first named member and an auxiliary device .fitting the interior of the tubular member.

In testimony whereof I aix m signature.

" EDWARD J. TIN.

the diaphragm and the arm, andan msu- Ill 

